Fuel Injection for a CJ-7
[an error occurred while processing this directive] Short Cuts

By: Jeff Layton - 5/2001

Plumbing the fuel lines and fuel pump would be a little more involved for Project Jeep Therapy because of the Vortec motor. The fuel injected engine requires high fuel pressure, much higher than a carborated engine, even higher than a throttle body injection. Many people with EFI conversions suffer fuel problems, I wanted to stay as factory as possible, so an in-tank pump was the only way to go. My time in the Navy also taught me a lot about NPSH, Net Positive Suction Head. A pump does not pull as well as it pushes, so having fuel around the pump not only cools it, but ensures good positive pressure at its outlet. Besides, Chevy put the pump in the tank, I would too. Pump replacement hassles would be solved later by a neat trick I learned in the 70's, stay tuned.

For now, I'm keeping the factory Jeep 20 gallon tank my CJ came with. John White of JB conversions assured me the lack of a sump in this tank wouldn't affect the operation of the soon-to-be in-tank pump.




graft2.jpg tank1.jpg tank2.jpg
The finished product looks almost factory, including the factory Chevy pump. The CJ tank's sending unit opening had to be opened up a little to fit the pump. The finished product, after cleaning, looks factory.
tankskid.jpg fuelline1.jpg fuelline2.jpg
Angle iron bent to beef up the gas tank skid plate Here's the Vortec Supply & Return lines adapted to braided "AN" style fittings with brass adapters. The fuel lines are routed inside the framerail for protection from exhaust heat.
adapter.jpg fuelline3.jpg clamp.jpg
Turning down the brass adapter Fuel filter mounting in front of the fuel tank Also visible in the picture is the new brakeline bracket, made to fit the SS lines better and allow more axle droop. Fuel injection hose clamp on the left, regular hose clamp on the right

First the pump needed to be retrofitted to the CJ sending unit, drawing the fuel off the bottom of the tank. After careful measurements, the section of the Chevy sending unit that holds the pump was grafted on the bottom of the CJ 20-gallon sending unit. Note the larger diameter fuel supply line, the Vortec return line is actually the OEM CJ supply line!

While I was at it, I thought I'd protect the CJ Plastic 20-gallon tank's thin 'skid plate'. Using a trick from a mid-1990's Top Truck winner, I bent some angle iron to help beef the skidplate some.

After considering several possibilities for routing fuel lines between the tank and motor, I decided on braided SS line. Earl's and Aeroquip are 2 popular competitors, and the local speedshop (Austin Performance) not only stocked the many parts & fittings, but were very knowledgeable in custom work.

As it turns out though, those brass adapters are not quite right for a Vortec, they are meant for a TPI motor and they are a little larger in diameter, but they can be easily turned down.

Adapting the fuel sending unit to the braided hose would haveto be accomplished through rubber EFI hose. A conversion fitting was purchased, and a conversion EFI fuel filter as well. The only good place I could find to mount the filter was in the rear, and a filter holder was fabricated out of a genuine Home Depot electrical conduit clamp! Electrical split-loom tubing was used to keep the abrasion to a minimum.

One last point to note, EFI fuel pressure is high. Be sure to use hoses rated for EFI (dollars per foot, not cents per foot). Also, EFI hose clamps are highly recommended and are available through NAPA. I double-clamped mine.


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